Resole resin binder composition

ABSTRACT

The invention relates to a binder composition comprising a low molecular weight resole resin in combination with boron compounds wherein said boron compounds are present in from about 1 to 30 parts per 100 parts by resole resin solids, said composition having a pH of about 2-6 and said resole having a viscosity of from about 5 to 5000 cps. Said binder provides laminates having superior electrical and flame retardant properties.

BACKGROUND OF THE INVENTION

In order to get acceptable processing speed from resole resinimpregnated substrates, it is common practice to use phenol-formaldehyderesoles which have high molecular weight, that is, they are reacted tonear the gel point in the preparation. These materials have to bedissolved in an organic solvent to provide viscosities low enough to beprocessable. The high viscosity leads to poor resin penetration intomany substrates, with the result being certain poorer properties of thefinished article such as water absorption and appearance. Also, duringresin preparation the resin high viscosity leads to poor heat transfer,longer resin cycles, and molecular weight distribution becomes toobroad.

Thus, in accordance with the present invention, resole resin bindercompositions are provided with greatly accelerated cure rates thatprovide laminates having excellent electrical and fire-retardantproperties. It has been discovered that the addition of 1 to 30 parts ofboron compounds per hundred parts of resole resin solids provides novelbinder compositions with great utility. Because of the boron additive,resole resins can be made of low molecular weight and narrow molecularweight distribution giving a more reliable, reproducible resin productin shorter cycles. No organic solvent need be used, eliminating a largepollution contributor. Penetration of this low molecular weight resininto any substrate is excellent. Processing speed is equal or bettercompared to currently used resole varnishes, and final laminated productproperties are better, especially electrical and flame resistanceproperties.

SUMMARY OF THE INVENTION

This invention relates to a binder composition comprising a lowmolecular weight resole resin and a boron compound curing accelerator,selected from the group consisting of boric acid, diammoniumtetraborate, diammonium octaborate, diammonium pentaborate and mixturesthereof, said boron compound being present in from about 1 to 30 partsby weight per 100 parts of resole resin solids, said composition havinga pH of about 2-6 and said resole resin having a viscosity of 5 to 5000cps.

DETAILED DESCRIPTION OF THE INVENTION Resole Resins

The phenol-formaldehyde resole resins of the present invention areprepared from a phenol selected from the group consisting of phenol,substituted phenols and substituted phenol mixtures and mixturesthereof.

The substituted phenols useful in the resins of this invention are allphenols that have at least one reactive position open in the ortho orpara position. Phenol and such substituted phenols or their mixtures canbe used. Substituted phenols include all phenols having at least oneattached radical selected from the group consisting of alkyl, aryl,cycloalkyl, alkenyl, cycloalkenyl, alkaryl, aralkyl, carbocyclic,halogen and mixtures thereof.

Examples of substituted phenols include: phenols substituted withstraight and branched chain alkyl radicals having 1 to 16 carbon atoms,e.g., cresol, isopropylphenol, 2,3-xylenol, 3,5-xylenol, 3,4-xylenol,2,6-xylenol, mono and disubstituted butyl, amyl, octyl, nonyl, decyl anddodecyl phenols; aryl substituted phenols, e.g., phenyl phenol andnaphthyl phenol; cycloalkyl phenols, e.g., terephenylphenols, e.g.,using limonene, pinene, methadiene, cyclohexyl and cyclopentyl;cycloalkenyl phenols, e.g., cyclopentenyl, dicyclopentadieneyl andmethacyclopentadieneyl phenols; alkenyl phenols, e.g., allylphenol,styrene, butenylphenol, pentenyl phenol, hexenylphenol; alkaryl phenols,e.g., tolylphenol, xylylphenol, propylphenylphenol; aralkyl phenols,e.g., benzyl, phenethyl, alphamethyl, phenylethyl, indyl and cymylphenols bisphenol A, bisphenol F, halophenols, e.g., chlorophenols,bromophenols, 2,4-dichlorophenol, 2,6,dichlorophenol, etc.

The substituted phenol mixture used to make such resin is prepared byreacting phenol under Friedel-Crafts conditions with controlled mixtureof carbocyclic compounds. The mixture of carbocyclic compounds comprises(on a 100 weight percent basis when in a form substantially free ofother materials);

A. from about 10 through 40 weight percent of compounds each molecule ofwhich has:

1. the indene nucleus,

2. from 9 through 13 carbon atoms,

3. as nuclear substituents from 0 through 4 methyl groups,

B. from about 5 through 70 weight percent of componds each molecule ofwhich has:

1. the dicyclopentadiene nucleus,

2. from about 10 through 13 carbon atoms,

3. as nuclear substituents from 0 through 3 methyl groups,

C. from about 15 through 65 weight percent of compounds each molecule ofwhich has:

1. a phenyl group substituted by a vinylidene group,

2. from about 8 through 13 carbon atoms,

3. as substituents from 0 through 3 groups selected from the classconsisting of methyl and ethyl,

D. from about 0 through 5 weight percent divinyl benzene;

E. provided that the sum total of all such compounds in any given suchmixture of carbocyclic compounds is always 100 weight percent.

Such substituted phenol mixtures and the resole resins preparedtherefrom can be prepared by methods disclosed in U.S. Pat. No.3,761,448.

Resole resins are easily made by reacting phenol and formaldehyde in thepresence of basic catalysts. Examples of low molecular weightphenol-aldehyde resole resins having characteristics suitable for use inthis invention are as follows:

EXAMPLE 1

Phenol (100 parts) 50 percent formalin (111 parts), and triethylamine (5parts) are charged to a vessel. The resulting mixture is reacted atabout 70° C. until the free formaldehyde content is less than about 4percent, after which the mixture is cooled. The product is a lowmolecular weight water soluble phenol-formaldehyde resole resin having81 percent solids, 9 percent H₂ O and a viscosity of 2400 cps.

EXAMPLE 2

Phenol (100 parts), 50 percent formalin (80 parts, and triethylamine (2parts) are charged to a vessel. The resulting mixture is reacted atabout 85° C. until the free formaldehyde content is less than about 2percent, after which the mixture is cooled. The product is a lowmolecular weight water soluble phenol-formaldehyde resole resin having78 percent solids, 8 percent H₂ O and a viscosity of 1100 cps.

EXAMPLE 3

Phenol (100 parts), 50 percent formalin (70 parts) and triethylamine (2parts) are charged to a vessel. The resulting mixture is reacted atabout 85° C. until the free formaldehyde content is less than about 1percent, after which the mixture is cooled. The product is a lowmolecular weight water soluble phenol-formaldehyde resole resin having74 percent solids, 4 percent H₂ O and a viscosity of 650 cps.

EXAMPLE 4

Phenol (100 parts), 50 percent formalin (111 parts) and calciumhydroxide (2.0 parts) are refluxed at 70° C. to a free formaldehydelevel of less than 4 percent. The resin is cooled and carbon dioxidebubbled into the resin to a pH of 7.0. The salt formed is filtered fromthe resin. The product is a clear, low molecular weight, water-solublephenol-formaldehyde resole resin having 83 percent solids, 7 percent H₂O and a viscosity of 3300 cps.

EXAMPLE 5

Phenol (100 parts), 50 percent formalin (111 parts) and 50 percentaqueous sodium hydroxide (4 parts) are refluxed at 70° C. to a freeformaldehyde level of less than 4 percent. The resin is cooled andphosphoric acid added to a pH of 7.0. The salt formed is filtered fromthe resin. The product is a clear, low molecular weight, water-solublephenol-formaldehyde resole having a solids of 80 percent, 7 percent H₂ Oand a viscosity of 3000 cps.

EXAMPLE 6

Cresol (40 parts), phenol (60 parts), 50 percent formalin (111 parts)and triethylamine (5 parts) are refluxed at 70° C. to a freeformaldehyde content of less than 4 percent, and the mixture cooled. Theresin is a low molecular weight phenol-formaldehyde resole producthaving a solids of 80 percent, 9 percent H₂ O and a viscosity of 2000cps.

Alkylated phenols of many types can be used to make low molecular weightresole resins. These substituted phenols are prepared by reacting phenolunder Friedel-Crafts conditions with an unsaturated compound or mixturesof such compounds.

To react phenol with such a compound mixture, it is convenient to useFriedel-Crafts conditions, as indicated.

The term "Friedel-Crafts conditions" as used herein refers to theconventional conditions known to those of ordinary skill in the art usedfor the alkylating or arylating of hydrocarbons (including phenol) bythe catalytic action of aluminum chloride or equivalent acid catalyst inthe presence of appropriate heat and pressure. In the practice of thisinvention, the phenol and suitable Friedel-Crafts acid catalyst aremixed, brought to the proper temperature, and the compound mixturemetered into the acidified (or catalyzed) phenol.

For purposes of this invention, the reaction of the compound mixturewith phenol is preferably carried out at temperatures in the range offrom about 25 to 200° C. although higher and lower temperatures can beused. Also, the reaction is preferably conducted under liquid phaseconditions at or below atmospheric pressure although superatmosphericpressures can be used.

Friedel-Crafts catalysts which may be used in place of aluminumchloride, or together with aluminum chloride, include:

A. Other inorganic halides, such as gallium, titanium, antimony and zinchalides (including ZnCl₂);

B. Inorganic acids such as sulphuric, phosphoric and the hydrogenhalides (including HF);

C. activated clays, silica gel and alumina;

D. BF₃ and BF₃ organic complexes, such as complexes of BF₃ with organiccompounds, such as ethanol, butanol, glycol, phenol, cresol, anisole,ethyl ether, isopropyl ether, di-n-butyl ether, formic acid, aceticacid, propionic acid and the like, or with inorganic acids, such asphosphoric acid, sulfuric acid, and the like, and

E. Alkyl, aryl and aralkyl sulfonic acids, such as ethanesulfonic acid,benzene sulfonic acid, benzene disulfonic acid, chlorobenzene sulfonicacid, 3,4-dichlorobenzene sulfonic acid, cresol sulfonic acids, phenolsulfonic acids, toluene sulfonic acids, xylene sulfonic acids,octylphenol sulfonic acid, -naphthalene sulfonic acid,1-naphthol-4-sulfonic acid, and the like.

When BF₃, as such, is employed, it is conveniently fed to a reactionmixture in gaseous form.

While any combination of compound starting mixture, phenol, and catalystcan be used, it is particularly convenient to react phenol with thecompound mixture in the presence of less than about 10 weight percent(based on the starting phenol) of acid catalyst. Typically, from about0.1 to 1 weight percent of Friedel-Crafts acid catalyst is employed(based on phenol).

The reaction mass is heated to a temperature in the range of from about25° to 200° C. The rate of this reaction is dependent, to some degree,on the temperature employed. In general, the reaction is rapid, and acomplete reaction between phenol and compound mixture is preferred.Generally, a total heating time of from about 10 minutes to 4 hours isemployed. The various process variables are summarized in Table I below.

                  TABLE I                                                         ______________________________________                                        Process     Broad         Preferred                                           variable    range         range                                               ______________________________________                                        Temperature About 25      About 40 to                                         (° C.)                                                                             to 200° C.                                                                           125° C.                                      Reaction    About 4       About 10 to                                         Time        hours         30 min.                                             Catalyst    Less than     About 0.1 to                                        (based on   about 10      1.0 weight                                          phenol)     weight        percent                                                         percent                                                           ______________________________________                                    

The properties of a given so-substituted phenol product are affected bythe process conditions used to make that product (e.g., molecular weightdistribution, color, and the like). The resulting reaction product is,as those skilled in the art will appreciate, a complex mixture ofvarious different substituted phenols produced from the reaction ofphenol under Friedel-Crafts conditions with the compound startingmixture to produce phenol molecules which are substituted on ring carbonatoms.

In general, to produce a resole for use in this invention, a phenol, asjust described, is neutralized under aqueous liquid phase conditions asby the addition of base and then from about 1.0 to 3.0 mols offormaldehyde per one mol of phenol is mixed with the phenol (now itselfa starting material). Water may be added with the formaldehyde. Formalinis preferred as a source for formaldehyde. Also, a basic catalystmaterial, such as ammonium hydroxide and/or amine selected from thegroup consisting of primary amines (such as ethylamine, isobutylamine,ethanol amine, cyclohexylamine, and the like); secondary amines (such asdiethanol amine, piperidine, morpholine, and the like); and tertiaryamines (such as triethylamine, triethanolamine, diethyl cyclohexylamine, triisobutyl amine; and the like) is introduced into the reactionmixture include metal oxides and hydroxides. Preferred amine catalystshave molecular weights below about 300 and more preferably below about200. The amine catalyst may include hydroxyl groups which tend topromote solubility of the amine in the reaction mixture. This basiccatalyst itself thus can be used to neutralize the starting substitutedphenol. The pH of this reaction mixture is maintained from (7.0 andpreferably above about 7.5) but below about 8.5. This reaction mixtureis then heated to temperatures of from about 60° to 100° C. for a timesufficient to substantially react most of the formaldehyde and therebyproduce a desired resole product. Times of from about 20 to 180 minutesare typical. Aqueous liquid phase preparation conditions are used.

It will be appreciated that the formaldehyde to phenol mol ratios hereindescribed have reference to the total amount of phenol present before areaction, including the phenol which is substituted by the compoundmixture as described above.

To optimize electrical properties in resoles used in this invention, itis preferred to use as a basic catalyst, when reacting such substitutedphenols with formaldehyde to make resole resins, one which is non-ionicand non-metallic in character.

The resole product produced by reacting the phenol with formaldehyde asdescribed above is one composed of methylolated substituted phenol whichhas been methylolated by the formaldehyde to a desired methylol content.As those skilled in the art fully appreciate, the methylol content andthe degree of advancement are readily controllable, so that one canoptimize such a resole resin for use in a particular application. Forpurposes of this invention, a phenol-formaldehyde resole resin or resolecan be regarded as being the reaction product of the above-describedphenols and formaldehyde under the aqueous base catalyzed conditions asdescribed herein which product can be thermoset by heat alone withoutthe use of a curing catalyst.

The following example shows how the low molecular weight, substitutedphenol resole resin is prepared.

EXAMPLE 7

Charge 100 parts phenol and 0.3 part concentrated sulfuric acid to areaction vessel and adjust the temperature to 75° C. Meter in 20 partsstyrene over 10 minutes. The reaction temperature will rise to 100° C.due to the exothermic reaction of styrene with phenol. Hold thetemperature mixture at 100° C. for 10 minutes, cool to 50° C. and add 5parts triethylamine, 80 parts formalin and react at 70° C. to a freeformaldehyde level of less than 2 percent. Dehydrate the resin to arefractive index of 1.559. The product is a clear, low molecular weight,water soluble resole resin made with phenol and styrene substitutedphenol.

The following examples are presented in tabular form. The process in allinstances is shown in Example 7 except that the indicated variables arealtered as shown in Table II below.

                  TABLE II                                                        ______________________________________                                               Unsaturated                                                                   Compound Mixture.sup.(1)                                               Example  Type        Amount      Temp. ° C.                            ______________________________________                                         8       1           30          100                                           9       2                                                                                          ##STR1##                                                                                  ##STR2##                                    10       3                                                                    11       4                                                                    12       5                                                                    13       6                       125                                          14       7                       100                                          15       8                                                                                                      ##STR3##                                    16       9                                                                    17       10                      125                                          ______________________________________                                         .sup.(1) Numbers listed under "Type Unsaturated Compound Mixture" each        designate a specific composition as shown below.                         

    1-       1     2      3    4    5   6    7   8   9   10                       ______________________________________                                        styrene  25                     5        50  50  50  50                       α-methyl                                                                styrene  25    100              5        50                                   vinyl                                                                         toluene  25           100       30           50                               indene   25                100  30               50                           dicyclo-                                                                      penta-                                                                        diene                           30  100              50                       ______________________________________                                    

All these resoles are characteristically one-phase, clear liquidsolutions, each having a viscosity ranging from about 5 to 500centipoises. The exact viscosity of a given solution depends upon manychemical process and product variables. For impregnating applications,viscosities of from about 50 to 2000 centipoises are preferred. Dilutionwith water or organic solvents is used to adjust the viscosity intopreferred ranges.

The total solids content of a given resole resin can be as high as about85 weight percent or even higher, and as low as about 20 weight percentor even lower, but preferred solids contents usually fall in the rangeof from about 25 to 75 weight percent.

When used for impregnation and reinforcing purposes, the resole resinsof this invention are useful for impregnating cellulosic paper, asbestospaper, and other non-woven sheet structures as well as woven fabrics(cotton, glass fibers, nylon, etc.), etc. Impregnation can beaccomplished by any convenient means, including dipping, coating,spraying, mixing or the like. The so-impregnated material is dried tolower the volatiles content and then heated to advance the resin to theproper degree for the intended use. The resoles of this invention areuseful in the preparation of laminates, such as those made from suchimpregnated sheet materials. Such laminates are used in electricalapplications as supports or as insulation for conductive elements. Thelaminates are generally manufactured in a sheet or block form which isthen punched or otherwise machined to provide desired configuration fora particular end use.

The resole resins of this invention are also useful in the manufactureof cloth laminates, and automotive oil filters. A suitable oil filtermedia, for example, is prepared by impregnating with a resole of thisinvention, cellulosic fiber paper modified with a synthetic fiber(polyester, or the like) and having a thickness of from about 5 to 20mils. Sufficient of the resole resin of this invention is used to obtainan impregnated sheet member having a cured resin content of about 35 to65 percent preferably about 15 to 25 percent, based on the weight of thepaper. After such paper is so impregnated, it is heated to advance theresin to a so-called B-stage, and then is corrugated or pleated to formthe filter element. The filter element is then assembled with the enduse filter container and heated to 250° F. to 350° F. for from 5 to 20minutes to cure the resin. When cured, the product has good flexibilityand low tendency to crack during use.

Boron Compound Accelerators

The accelerators employed in the composition of the present inventionare boron compounds selected from the group consisting of boric acid H₃BO₃, diammonium tetraborate (NH₄)₂ O2B₂ O₃.4H₂ O, diammonium octaborate(NH₄)₂ O4B₂ O₃.6H₂ O, diammonium pentaborate (NH₄)₂ O5B₂ O₃.8H₂ O andmixtures thereof. Such preferred boron compounds are described in theEncyclopedia of Chemical Technology, 2nd Edition, 1964, IntersciencePublishers, New York, N.Y., Vol. 3, pages 609-648.

Boron compounds as described are added to the resins described in theexamples to give the desired properties of lower dry rubber for fasttreating yet retain low molecular weight for good impregnation into avariety of substrates, enhanced electrical properties, no organicsolvent needed for lower pollution potential and better flameresistance.

The amount of boron compound can vary from about 1 part per 100 resinsolids to about 30 parts (same basis). Preferably, between 2 and 10parts are needed to obtain the desired end results listed above.Excessive amounts of boron compounds are not soluble or if soluble,crystallize out when cold. When boric acid or the ammonium borates areused alone, the pH of resoles is usually about 2-6. This may lead tocorrosion and the above mentioned insolubility in certain resoles. Thisproblem is solved by raising the resin mixture pH with ammoniumhydroxide to about 7-10. Dry rubber lowering effectiveness is reducedonly slightly, and corrosion to metals such as iron is avoided andcompatibility is improved.

The boron compounds are dissolved in the resole resins by conventionalmixing as can be appreciated by those skilled in the art. The solutionsformed are stable at temperatures usually used for storing and shippingresole resins binder compositions.

Binder Compositions

The binder composition has, in combination, a resole resin comprisingresin solids of from 20 to 85 percent, preferably 25 to 75 percent, byweight, a dissolved water content of 0.5 to 35 percent, preferably 2.0to 15 percent by weight based on said resole resins solids, said resolehaving a viscosity of from about 5 to 5000 cps preferably 50 to 700 cps,said composition having present from about 1.0 to 30 parts, preferably 2to 10 parts of a boron compound based on said resole resin solids.

The binder composition can be a solution wherein said resole resin andaccelerator are contained in a solution comprising about 20 to 98percent, preferably 25 to 75 percent by weight of resin solids, about 2to 80 percent, preferably 25 to 75 percent by weight water and about 0.5to 5 parts preferably 1 to 3 parts of a boron compound based on saidresin solids.

The binder composition can be a solution or varnish wherein said resoleresin and accelerator are contained in a solution comprising:

A. about 20 to 85 percent by weight of resole resin solids,

B. about 0.5 to 15 percent by weight of water,

C. about 0.5 to 5 parts by weight accelerator per 100 parts of resoleresin solids, and

D. the balance up to 100 percent by weight of said solution being anorganic liquid which

1. is substantially inert to said resin and water,

2. evaporates below about 150° C., at atmospheric pressures,

3. is a mutual solvent for said resin, said water and said accelerator,being present in an amount sufficient to maintain a solution.

The organic liquid is a relatively volatile, inert organic solventmedium having the properties described above. While the organic liquidused has properties as indicated above, it will be appreciated that suchliquid can comprise mixtures of different organic liquids. Preferredliquids are lower alkanols (such as ethanol and methanol) and loweralkanones (such as acetone or methyl ethyl ketone). The term "lower"refers to less than 7 carbon atoms per molecule as used herein. Aromaticand aliphatic (including cycloaliphatic) hydrocarbons can also beemployed as solvents for a given resin, including benzene, toluene,xylene, naphthylene, nonane, octane, petroleum fractions, etc.Preferably, the total water content of a solution of the invention isbelow about 15 weight percent, and more preferably falls in the range offrom about 0.5 to 5 weight percent.

Those skilled in the art will appreciate that care should preferably betaken to use an organic liquid system in which the phenolic resoleresins are completely soluble as well as any water present. Adding, forexample, a ketone or an ether-ester solvent like butyl Cellosolve willgenerally improve the water tolerance (ability to dissolve water) of asolvent system.

EMBODIMENTS

The following examples are set forth to illustrate more clearly theprinciples and practices of the invention to one skilled in the art.They are not intended to be restrictive but merely to be illustrative ofthe invention. Unless otherwise stated herein, all parts and percentagesare by weight.

Dry rubbers of other phenolic resin resole mixtures with acids andammonium salts of acids were run to determine how broadly the dry rubberlowering effect was. Please see attached Table III. Dry rubbercorrelates with process speed. Oxalic acid, benzoic acid, acetic acidand lactic acid give increased dry rubbers at 3.3-5.1 pH, whereassulfamic acid gave much lower dry rubber at 7.5 pH (compared to thecontrol at pH 8.2). Sulfuric acid and phosphoric acid gave reduced dryrubbers at low pH. Thus, there is no correlation of pH and dry rubber.Of all the ammonium salts tested, ammonium borate gave the most dryrubber lowering and also was the only salt to give low pH (3.0). Allother salts gave >5.7 pH. Since boric acid is very weak, the low pH isattributed to the presence of polyhydroxy compounds forming a strongeracid with one monoborate ion B(OH)₄ ⁻ and two molecules of polyhydroxycompound. When running dry rubbers on resin mixtures it was noted thatNH₄ borates and boric acid were the only additives to give a rapidmolecular weight build-up on the cure plate. All other additives shownon the Table were of low viscosity for most of the test and then rapidlygelled.

It is evident that none of the substances tested in Table III (exceptborates) will give the combination of fast processing, betterelectricals and flame resistance.

                                      TABLE III                                   __________________________________________________________________________    EXAMPLES 1 - 39                                                               Dry Rubber/pH with Selected Acid and Salts and Phenolic Resole                     Amount (per 100      pH (with                                            Example                                                                            resin resole)                                                                           Acid       added H.sub.2 O)                                                                     150° DR                                                                     K                                       __________________________________________________________________________    1    0        control.sup.(1)                                                                           8.2    203                                          2    4        oxalic      3.3    278  (K.sub.1 = 6.5 × 10.sup..sup.-                                          2                                       3    8        oxalic      1.8     38  (K.sub.2 = 6.5 × 10.sup..sup.-                                          5                                       4    4        lactic      5.1    225                                                                                1.4 × 10.sup..sup.-4              5    8        lactic      3.6    189                                          6    4        benzoic     5.1    285  1.5 × 10.sup..sup.-5              7    4        acetic      4.5    259  1.8 × 10.sup..sup.-5              8    2.5      sulfamic    7.5    132                                          9    0        control.sup.(2)                                                                           8.2    285                                          10   2        phosphoric  2.7    145  (K.sub.1 = 7.5 × 10.sup..sup.-                                          3                                                                             (K.sub.2 = 6.2 × 10.sup..sup.-                                          8                                                                             (K.sub.3 = 4.8 × 10.sup..sup.-                                           13                                     11   2.5      sulfuric    1.1     25  (K.sub.1 =  4 × 10.sup..sup.-1                                          (K.sub.2 = 1.2 × 10.sup..sup.-                                          2                                       12   1.3      sulfuric    2.2     90                                          13   1.16     sulfuric    7.3    215                                          14   1.0      sulfuric    7.5    --                                           15   0        control.sup.(3)                                                                           8.2    203                                          16   1        boric       7.7    180  5.8 × 10.sup..sup.-10             17   2        boric       2.9    140                                          18   4        boric       2.4     80                                          19   8        boric       2.0     40                                          20   0        control.sup.(4)                                                                           8.2    285                                          21   4        ammonium acetate                                                                          8.2    255                                          22   4        ammonium formate                                                                          6.1    207                                          23   4        ammonium sulfamate                                                                        6.9    205                                               Amount (per 100      pH (with                                            Example                                                                            resin resole)        added H.sub.2 O                                                                      150° DR.sup.6                                                               K                                       __________________________________________________________________________    24   4        ammonium citrate                                                                          6.0    197                                          25   4        ammonium nitrate                                                                          6.0    176                                          26   4        ammonium tartrate                                                                         6.5    174                                          27   4        ammonium chloride                                                                         5.7    165                                          28   4        ammonium oxalate                                                                          6.8    154                                          29   4        ammonium sulfate                                                                          5.9    145                                          30   4        diammonium phosphate                                                                      7.1    136                                          31   4        ammonium pentaborate                                                                      3.0    110                                          32   4        ammonium biborate                                                                         3.0    110                                          33   0        control.sup.(5)                                                                           8.2    285                                          34   2        NaH.sub. 2 PO.sub.4                                                                       7.7    285                                          35   2        NH.sub.4 H.sub.2 PO.sub.4                                                                 6.8    190                                          36   2        (NH.sub.4).sub.2 HPO.sub.4                                                                7.2    175                                          37   4        (NH.sub.4).sub.2 HPO.sub.4                                                                7.0    136                                          38   2        Na.sub.3 PO.sub.4                                                                         8.5    155                                          39   2        H.sub.3 PO.sub.4                                                                          2.7    145                                          __________________________________________________________________________     .sup.(1) Resin A slightly advanced                                            .sup.(2) Resin A                                                              .sup.(3) Resin A slightly advanced                                            .sup.(4) Resin A                                                              .sup.(5) Resin A                                                              .sup.(6) DR - dry rubber test-composition spread on hot plate at desired      cure temperature and worked with a spatula until no viscous strings form      on removal of spatula. Time in seconds to reach rubbery state determines      rate of cure.                                                            

Phenolic resin resole laminates have faster treating, improvedelectricals and improved flame resistance when boric acid is added ascompared to standard phenolic varnish, and resoles without boric acid.

Examples 40 to 46 and Table IV are shown below illustrating the effectsof boric acid on several resole resins.

                                      TABLE IV                                    __________________________________________________________________________    EXAMPLES 40 - 46                                                              Examples     40   41        43   44   45   46                                 Resin        Phenol-formaldehyde resole.sup.(7)                                                           Resole.sup.(6)                                                                     Alkylated                                                                          P/F  Resole.sup.(8)                     __________________________________________________________________________    Boric acid,                                                                   parts/100 resin                                                                            0    5    10   0    0    7    9                                  160° C. dry rubber,                                                    seconds      178  55   40   50   160  60   50                                 B-stage time.sup.(1),                                                         minutes      17   4    4    4    20   41/2 41/2                               Water Absorption.sup.(2),%                                                                 0.9  0.9  1.2  0.7  0.3  0.5  0.7                                Dielectric A.sup.(4)                                                                       5.7  5.0  4.4  5.2  4.7  4.2  3.9                                Constant at D24/23.sup.(2)                                                                 6.0  5.3  4.7  5.4  4.8  4.3  4.0                                10.sup.(6) cps                                                                Dissipation A.sup.(4)                                                                      .047 .044 .038 .040 .038 .036 .029                               Factor at D24/23.sup.(2)                                                                   .051 .046 .045 .045 .039 .038 .032                               10.sup.(6) cps                                                                Underwriter's Lab                                                                          BURNS                                                                              17(37)                                                                             16(19)                                                                             BURNS                                                                              BURNS                                                                              17(28)                                                                             13(16)                             Flame Test, seconds.sup.(3)                                                   Insulation Resistance                                                                      4.5 x                                                                              1.1 x                                                                              3.4 x                                                                              --   1.3 x                                                                              3.3 x                                                                              1.3 x                              megohms Cond. A.sup.(4)                                                                    10.sup.6                                                                           10.sup.7                                                                           10.sup.7  10.sup.7                                                                           10.sup.7                                                                           10.sup.8                           __________________________________________________________________________     Footnotes:                                                                    .sup.(1) 135° C. air oven, time to acceptable flow                      laminate resin contents - 54-57%                                              paper used - cotton linter                                                    cure conditions - 30 minutes/150° C./1000                             .sup.(2) 24 hours in 23° C., water = D24/23                            .sup.(3) () = highest number, test number is average of six 10"               .sup.(4) Cond. A = as is                                                      .sup.(5) Loss Index = product of dielectric constant and dissipation          factor                                                                        .sup.(6) alkylated phenolic resole high molecular weight resin - viscosit     of 25,000 cps with about 7 percent H.sub.2 O                                  .sup.(7) RESIN EXAMPLE B                                                      .sup.(8) RESIN EXAMPLE L                                                 

It is evident from Example 43 that advanced resole resins providelaminates with poorer electrical properties as compared to the lowviscosity resoles of the present invention used in combination with saidboron compounds, as accelerators.

EXAMPLES 47 - 51

The resin of Example 3 (100 parts) was used in combination with boricacid to prepare binder compositions. The pH of binder composition wasadjusted with ammonium hydroxide to test curing rates and ironcorrosion. Table V below shows the results of these tests.

                  TABLE V                                                         ______________________________________                                                Boric                  150° C.                                                                        Iron                                   Example Acid     NH.sub.4 OH                                                                            pH   DR      Corrosion                              ______________________________________                                        47      0        0        7.9  540     none                                   48      8        0        2.6  130     yes                                    49      8        yes      5.7  130     yes                                    50      8        yes      6.9  105     slight                                 51      8        yes      8.2  105     none                                   ______________________________________                                    

It is evident that curing rate of the composition is retained at highlevels with boric acid accelerators in the presence of NH₄ OH withcorrosion being controlled at higher pH values of greater than 7.

EXAMPLES 52 - 53

Examples 47-51 were repeated using 8 parts of ammonium tetraborate andammonium pentaborate respectively. The pH of the compositions were foundto be about 3. The compositions were adjusted to a pH of about 8 and thedry rubber rates were found to be about 120 seconds with a control ofabout 450 seconds showing that NH₄ OH can be used to adjust pH into therange of 7-10 without affecting cure rate.

What is claimed is:
 1. A non-corrosive binder composition comprising alow molecular weight resole resin and a boron compound curingaccelerator, selected from the group consisting of boric acid,diammonium tetraborate, diammonium octaborate, diammonium pentaborateand mixtures thereof, said boron compound being present in from about 1to 30 parts by weight per 100 parts of resole resin solids, saidcomposition having a pH of about 7-10 by the addition of sufficientammonium hydroxide to raise the pH to about 7-10 and said resole resinhaving a viscosity of 5 to 5000 cps.
 2. A binder composition of claim 1,wherein the boron compound is present in from about 2 to 10 parts byweight of boron compound per 100 parts of resole resin solids.
 3. Abinder composition of claim 1, said resole resin comprising the reactionproduct of formaldehyde and a phenol, said phenol selected from thegroup of phenol, substituted phenols, substituted phenol mixture andmixtures thereof in a mol ratio 1.0 to 3.0, reacted in the presence of abasic catalyst.
 4. A binder composition of claim 2, wherein saidsubstituted phenol mixture has been prepared by alkylation of phenolwith a mixture of carbocyclic compounds under acid conditions at atemperature in the range of 25° to 200° C., whereby 10 to 80 parts byweight of the mixture of carbocyclic compounds reacts with 100 parts byweight of phenol, said mixture of carbocyclic compounds comprising:A.from 10 to 40 parts by weight of compounds each molecule of which has:1.the indene nucleus,
 2. from 9 to 13 carbon atoms,
 3. as nuclearsubstituents from 0 to 4 methyl groups; B. from 5 to 70 parts by weightof compounds each molecule of which has:1. the dicyclopentadienenucleus,
 2. from 10 to 13 carbon atoms,
 3. as nuclear substituents from0 to 3 methyl groups; C. from 15 to 65 parts by weight of compounds eachmolecule of which has:1. a phenyl group substituted by a vinylidenegroup,
 2. from 8 to 13 carbon atoms,
 3. as substituents from 0 to 3groups selected from the class consisting of methyl and ethyl; and D.from 0 to 5 parts by weight of divinyl benzene.
 5. A binder compositionof claim 2, wherein said phenol is phenol.
 6. A binder composition ofclaim 2, wherein said phenol is a substituted phenol having at least oneradical selected from the group consisting of alkyl, aryl, cycloalkyl,alkenyl, cycloalkenyl, alkaryl, aralkyl, carbocyclic, halogen andmixtures thereof.
 7. A binder composition of claim 3, wherein said basiccatalyst is selected from the group consisting of ammonium hydroxide,hexamethylene tetramine and triethylamine.
 8. A binder composition ofclaim 1, wherein said boron compound is boric acid.
 9. A bindercomposition of claim 1, wherein said boron compound is diammoniumtetraborate or diammonium pentaborate and mixtures thereof.
 10. A bindercomposition of claim 1, wherein said resole resin comprises a solidcontent of from about 20 to 85 percent by weight, a water content of 2to 35 percent by weight based on said resole resin, a viscosity of 5 to5000 cps, said boron compound being present in from about 1 to 30 partsbased on 100 parts of resole resin solids.